Coil system more particularly for highfrequency heating generators



June 3, 1958 L. BLOK ET AL 2,837,725

COIL SYSTEM MORE PARTICULARLY FOR HIGH-FREQUENCY HEATING GENERAToRs Filed Dec. 30. 1953 2 Sheets-Sheet 1 IN VEN TORS LOURENS BLOK GOOITZEN ZWANENBURG AGENT June 3, 1958 L. BLOK ETAL 2,837,725

COIL SYSTEM MORE PARTICULARLY FOR HIGH-FREQUENCY HEATING GENERATORS Filed Deo. 30, 1955 2 Sheets-Sheet. 2

LOURENS BLOK GOOITZEN ZWANENBURG AGENT the coil system at the lower and upper side of the bed plate 31. All these parts may be of usual construction and are consequently not shown in the drawings.

The primary coil 35 is a copper tube, for example 6 mm. thick. lt is helically wound and supported by three insulating rods 39, 4l, 43, for example made from hard paper and resting against the inner side of the coil. The ends of these rods are secured, for example by means of wedges, in two insulating end plates 45 and 47. Situated between the rods 39, 41, 43 is a substantially cyiindrical ferromagnetic core 49 of cubic ferrite material with low losses (mixed crystals of iron oxide and other metal oxides), which material is a poor conductor of electricity. The core 49 is furnished with three long axial slots in which the rods 39, 41, 43 are partly sunk, the diameter of the core being a few mm. smaller than the inside diameter of the helix 35.

The assemblage of helix 35, core 49, supporting rods 39, 41, 43 and bed plates 45, 47 is slidable as a whole over a guide bar 5l of electrically non-conductive material, for example hard paper of unround, for example, rectangular cross-section, which bar passes substantially co-axially through the end plates 45, 47 and through the core 49. To this end, the end plates 45, 47 are provided with mating apertures, the core 49 having a spacious axial bore through which also passes one of the supply ducts (53) of the coil 35.

The coupling coil 37 mainly consists of a curved copper strip which surrounds the coil 35 with a few mm. of intermediate space and is supported by two fiat trapezium-shaped insulating supports, 55, 57. The width of the strip-i. e. the axial length of the coupling coil-is approximately equal to the length of the coil 35. The core 49 is approximately 20% longer. Besides constituting the coupling turn 37, the strip also constitutes the double supply duct of this turn. The two ends 59, 61 (Fig. 3) of the strip extend parallel to each other with a few mm. of intermediate space, project obliquely from the oil container 33 and are terminated by heavy clamps 63 and 65. These clamps, together with the edges 59 and 61 of the strip are screwed in an insulating manner to a bracket 67 welded to the container 33.

Through the helix 35 ows water, which is supplied through tubing 69 and 71 and serves to cool the coil as well as the oil surrounding it, this oil cooling, in its turn, the core 49. The heat evolved due to loss of energy in said component parts may thus be safely carried off. In order to cool the coupling coil 37 the copper strip 37, 59, 61 has soldered to it tubes 73 and 75 which may be connected to the cooling water duct, if desired in series with coil 35.

Adjustment of the coupling between the primary coil 35 and the secondary coil 37 is eected by means of a handwheel 77, a roller 79 seated on its shaft and two metal bands 81, S3 adapted to be wound on said roller, this device permitting the primary coil to be axially displaced. For this purpose the band 81 is secured with one end to the roller 79 and passes over a roller 87, freely rotatable in an opening 85 of the plate 31, through the opening S5 and along the bottom of the plate to the end plate 45. The band S3 similarly passes over a roller 89, through an opening 91 and through slots (not visible in the drawing) of the supports 55, 57 equally to the end plate 45. The two bands are lightly tautened and on operating the hand-Wheel 77 one of the bands is unwound from the roller 79, Whereas the other band is wound up.

By disposing of the current and cooling water supply duct 53 inside the core 49 the construction-length of the coil system be minimized, otherwise this duct wouid proiect beyond the end plate 47 over a length equal to the distance over which the coil 35 is displaceable.

in order to prevent the supply duct Si attaining a comparatively high self-induction, which would act as an f unwanted leakage inductance owing to the surrounding `ferromagnetic material of the core 49, this core is provided with a radial saw-cut 93 which forms an interruption of the magnetic circuit present around the duct 5i.

What is claimed is:

l. A coil system for high frequency heating generators comprising a substantially cylindrical container of electrically insulating material, a helically wound, watercooled primary coil in said container and extending coaxially with said container, a ferromagnetic core having an axial bore and a radial gap therein, means mounting said ferro-magnetic core axially within said primary coil, a coupling coil secured to the outer surface of said cylindrical container extending co-axially therewith and substantially surrounding said primary coil, a plurality ot current and cooling water supply ducts for said primary coil, one of said supply ducts passing through the axial bore of said ferromagnetic core, and the magnetic circuit formed by said core around said one of said supply ducts being interrupted by said radial gap.

2. A coil system as set forth in claim l wherein said container has oil therein and at least said primary coil and said core are disposed therein.

3. A coil system for high frequency heating generators as claimed in claim l wherein said coupling coil includes an arcuate metal strip substantially bent around said container and closely surrounding the primary coil.

4. A coil system as set forth in claim 1 wherein said primary coil is arranged vertically and the supply ducts pass through the top wall of said container in an oiltight manner, said top wall being co-axial with said primary coil. i

5. A coil system as set forth in claim l wherein said container is substantially cylindrical and constituted of a silica-containing material.

References Cited in the le of this patent UNITED STATES PATENTS 685,012 Tesla Oct. 22, 1901 1,382,905 Gravell June 28, 1921 2,314,865 Bierwirth Mar. 30, 1943 2,366,290 Rudd Ian. 2, 1945 2,404,404 Roberds July 23, 1946 

